Signaling system for telephone-exchanges.



No. 763,803- PATENTED JUNE 28, 1904.

c. ELSORIBNER.

SIGNALING SYSTEM FOR TELEPHONE EXCHANGES.

APPLICATION FILED OUT-2 19011 N0 MODEL. I

Wltnesses:

82/. W, V,- c araesgscribner,

lmventcprz THE NORRIS PETERS co. PHOTO-LIYHO.. WASHINGTON n. c.

UNITED STATES Patented June 28, 1904.

PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

SIGNALING SYSTEM FOR TELEPHONE-EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 763,803, dated June 28, 1904.

Application filed October 26, 1901. Serial No. 80,042. (No model.)

To all whom it may concern:

Be it known that I, CHARLEs E. SCRIBNER, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Signaling Systems for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description.

My invention relates to a telephone-exchange system, and is applicable more particularly to a system wherein local batteries are employed at the substations for supplying current to the subscribers transmitting-telephones, my object being in general to provide for automatic signaling without requiring a continuous flow of current in the line during the connection, which has been necessary in most of the automatic signaling systems heretofore devised. 7

Another feature of my invention is a combined ringing-key and electromagnetic supervisory signal associated with the central-ofiice operators plug-circuit, by which lines are temporarily connected together.

I will describe my invention by reference to the accompanying drawing, which is a dia gram illustrating two telephone-lines extending from substations to a central oflice, with a pair of plugs and their plug-circuit for uniting the lines, the system being organized and equipped in accordance with my invention.

The features or combinations which I regard as novel will be pointed out in the appended claims.

Each line extends in two limbs 1 2 from the substation apparatus to the line-springs of a spring-jack a at the central oflice, the circuit of the line being completed through the normal resting contacts'of the spring-jack to the poles of a central battery I). The positive pole of the battery, which is connected with the limb 1 of the line, is grounded. An electromagnetic line-signal c, which is preferably of high resistance, is included in the line-circuit between the battery and contacts of the springjack. The armature of the line-signal magnet, besides operating the shutter or target of the signal, is adapted when drawn up to close a switch-contact which controls a local circuit lncluding the magnet-w1nd1ng, said local circuit being controlled at normal resting conof the line, said bridge, however, being maintained open as to steady currents by a condenser d, which will transmit the varying telephonic current, but which prevents the passage of steady current. A gravity telephoneswitch e-is provided for cutting the telephone apparatus into and out of circuit in the usual way. In addition to the ordinary contacts of this telephone-switch I provide an additional contact-springe, which is grazed by an extension of the switch-lever as the latter moves up or down. The switch-lever is connected with the limb 2 of the telephone-line, and the contact-spring e is connected with the earth, so that as the telephone is taken from its hook or replaced thereon the circuit of the limb 2 will be momentarily closed by the passing contact as the extension of the switch-lever grazes the end of the spring 6. The magnet-winding of a relay f is included in the circuit between the limb 2 of the telephone-line and the switchlever c, said relay thus being in the path of the battery-current, which flows when the circuit is closed at c. The switch-contacts of the relay f, which are closed when said relay is excited, control a conductor 4, which extends from the end of the winding of said relay direct to the grounded limb 1 of the telephone-line, form-.- ing a bridge of the circuit independent of the telephone-switch. It will be seen that when the relay is once excited by the closing of the circuit at c it will tend to lock itself up and to maintain the circuit by way of conductor 4 unless the current is cut ofl or diverted, as by the short circuit 3 at the central oilice.

The apparatus at substation B is of the same general type as that at station A, but is provided with an additional contact (Z for the telephone-switch, closed when the telephone is off the hook. This contact (Z controls a short circuit 8 about the magnet-winding of the relay f. The purpose of this short circuit will be explained hereinafter.

At the central office I have indicated a pair of plugs and their plug-circuit for uniting lines. The plug g is the answering-plug and h is the calling-plug. Each plug has two contacts adapted to engage respectively with the line-springs of any spring-jack into which it may be inserted, and the contacts of each plug are connected with the corresponding contacts of its mate by the link conductors 5 6 of the plug-circuit. A ringing-key is provided for controlling the connection of the ringing-generator G with the calling-plug, and a supervisory-signal device may be combined with this ringing-key, as shown in the drawing. The ringing-key has the usual pair of switchsprings in k, which are connected, respectively, with the conductors 5 and 6 leading to the terminal pieces of the calling-plug. These switch-springs normally rest against inner contact-anvils which form the terminals of the portions of the plug-circuit conductors leading to the answering-plug. The actuating-plunger Z of the ringing-key carries an insulating-wedge, which when the plunger is depressed is forced between the springs in separating said springs from their normal resting contacts and forcing them against outer contact-anvils which are connected, respectively, with the poles of the generator G. The outer contact of spring Z: is connected directly to one pole of the ringing-generator; but the outer contact of the other spring, 71:, is connected to the other or grounded pole of the generator through a conductor 7, which includes an electromagnet m and the battery 7). The grounded pole of the battery 6 is also permanently connected with the portion of the plug-circuit conductor 5 which leads to the answering-plug, so that said battery is thus in a bridge of the plug-circuit, an impedance-coil a being interposed between the grounded pole of the battery and the plugcircuit conductor 5, and the winding of magnet m, which is of high impedance, being interposed between the free pole of the battery and the conductor 6.

While for convenience of illustration three batteries are shown in the drawing, it is understood that a single central battery may be employed, connected as indicated.

The armature-lever of the magnet on operates a shutter or target m, which is displayed when the armature is attracted, and said armature also carries a detent m which is adapted to engage an extension carried by the plunger of the ringing-key to hold said ringing-key in its depressed condition. WVhen the plunger Z of the ringing-key is depressed, the

armature of the magnet m is pushed over part way, so that the signal at is half displayed, and the detent m engages the arm carried by the plunger and holds it so that the key will be set and the ringing-current will be continuously applied to the line until the magnet m shall be excited and trip the key.

It is understood, of course, that the operator may be provided with the usual telephone set and a key for bringing the same into connection with any of the plug-circuits which she maniplates, but this apparatus is omitted from the drawing for clearness.

The operation of the system may be traced as follows: When a subscriber at one of the substations desires an exchange connection, he transmits a signal to the central office by simply removing his telephone from its switchhook. The passing contact of the switch-lever with the spring 0 causes a momentary flow of current in the line, which excites the magnet of the signal 0 and causes the same to draw up its armature. The short circuit 3 is thus closed, and the signal is locked in its excited position subject only to the breaking of the circuit at the contacts of the spring-jack. The magnet of relay f at the substation will be excited simultaneously with the magnet 0; but the relay, however, will not be maintained excited, since it is immediately short-circuited by the switch-contact of the signalmagnet c. In case the additional contact (Z is provided, as shown at substation B, the relay f will also be short-circuited at this contact. The central-office operator, perceiving the signal, inserts her answering-plug 9 into the spring-jack of the calling-line and bringing her telephone into circuit in the usual way inquires the number of the subscriber wanted. Having received this information, she inserts the calling-plug it into the springjack of the line wanted and depresses the plunger Z to transmit a call-signal. The insertion of the answering-plug g into the spring-jack of the calling-line separates the line-springs of the spring-jack from their nor mal resting contacts and cuts ofl the battery 6 and signal 0 from connection with the line, the local circuit 3 being broken, so that the line-signal is eflaced. The battery 5 is, however, brought into connection with the line by way of the plug-circuit, said battery being bridged between conductors 5 and 6, with the impedance-coil a on one side and the magnet at on the other side. The plug and springjack are so constructed that the sleeve of the plug which is connected with the free pole of the battery will not touch the longer linespring of the jack until said line-spring has already been raised from its resting contact to cut off the line-signal, and when the plug is withdrawn the battery will be disconnected by way of the plug-circuit before it is applied at the resting contacts of the jack. Although the battery 6 1s connected in a bridge of the plugcircuit with the magnet m, said magnet will not receive current when the answering-plug is inserted in the jack of the calling-line, since the circuit of that line is open at the substation, the contact 6 having been closed only for an instant as the telephone was taken from its hook. When the plunger Z of the ringingkey is depressed, the springs Z4 K0 are forced apart, breaking engagement with their normal resting contacts and engaging the outer springs, which are connected, respectively, with the poles of the generator G. Callingcurrent is thus applied to the called line over conductor 5 of the plug-circuit, and after passing out over the line through the subscribers call-bell and back to the conductor 6 of the plug-circuit passes thence through magnet on and battery 6 to earth. The resistance of the call-bell is, however, so great that the ringing-current passing through the magnet on is not sufficiently strong to cause the attraction of the armature. When the called party answers by removing his telephone from its hook, the circuit of conductor 2 of the called line is momentarily closed by the passing contact a, and an impulse of steady current from the battery I) is permitted to flow over the circuit, energizing the magnet 77?. and causing the same to draw up its armature. The detent m is thus withdrawn from its engagement with the-extension of the plunger Z, and the ringing-key is thus released or tripped, so that the springs [6 7c resume their normal positions. The circuit of the battery and the generator G is thus broken at the outer contacts of the ringing key, and the switchsprings k k move back against their normal resting contacts, completing the circuit from one plug to the other. As soon as the springs k /c' touch their inner contacts the battery is again applied in a bridge of the plug-circuit between the magnet m and the impedancecoil; but during the momentary interval after the switch-springs have left their outer contacts and before they strike their inner contacts the battery is cut off from the called line. During this interval the armature of the relay f at the called station, which may have been drawn up as the switch-lever passed the contact a, will fall back, leaving the linecircuit open, so that when the contact is made at the inner anvils of the switch-springs In k the battery will find no circuit over the called line. If the telephone-switch at the called station is provided with the contact (Z the switch-lever will strike this contact an instant after the passing contact a is'rnade, and the relay will thus be short-circuited by the conductor 8. In any event the target 977/ will not be displayed except for an instant as the ringing-key is tripped. The ringing-key should be designed to act rather sluggishly, so that the armature of relay f will have time to be retracted before the springs 71; is move from their outer to their inner contacts. When either one of the subscribers has finished conversation and replaces his telephone upon its hook, the passing contact which is made in the movement of the switch-lever closes the circuit momentarily, and relay f being in this circuit and not being short-circuited draws up its armature and maintains the bridge 4 closed, so that current from battery 5 will flow continuously over the line and through the magnet on, causing the continued display of the target m. The display of this target indicates to the operator that the conversation is finished and that the connection may be taken down.

The contact (Z at the substation, which may be used or not, as desired, makes it possible for the subscriber to intermittently display the supervisory signal m to attract the attention of the operator, as in making a recall. It will be seen that when the telephone at substation B is placed on its hook it will close the circuit, and if the telephone stays on the hook the relay f will be excited to maintain the circuit closed, and so to maintain the excitement of the supervisory-signal magnet m; but if the telephone is then lifted from the hook again the relay will be short-circuited at the contact d and will allow its armature to drop back and open the circuit whereby magnet m at the central ofiice is deprived of current. As the switch-hook is vibrated up and down the circuit may thus be intermittently closed and broken and the supervisory signal intermittently displayed.

Having thus described my invention, 1 claim 1. The combination with a telephone-line extending from a substation to a central ofiice, of a battery connected with the line at the central office, a telephone-switch at the substation having a contact closed momentarily at each oscillation of the switch-lever, said contact controlling the circuit of the battery-current in the line, a signal-controlling magnet at the central ofiice in the path of current so controlled, a relay at the substation in the battery-circuit controlled by said switch, contacts operated by the relay adapted to close the battery-circuit throughits own magnet-winding independently of said telephone-switch, and means for shunting or short-circuiting said relay, substantially as set forth.

2. The combination with a telephone-line extending from a substation to a central office, of abattery connected with the line at the central ofiice, a telephone-switch at the substation having a contact closed momentarily at each oscillation of the switch-lever, said contact controlling the flow of battery-current in the line, a line signal-magnet at the central ofiice in the path of current so controlled, a relay f in the path of current at the substation, switch-contacts operated by the relay for closing the circuit through the same independently of the telephone-switch,aspringjack for the line, a plug and plug-circuit for making connection therewith, a supervisory signal and a source of current associated with the plug-circuit, brought into connection with the telephone-line in registering contacts of the plug and spring-jack, a shunt of the relay f, and means for closing said shunt after the line-circuit has been momentarily closed at the telephone-switch in initiating a call.

3. The combination with a telephone-line extending from a substation to a central oflice, of a source of current and a signal-controlling magnet in the line-circuit at the central oflice, a telephone-switch at the substation normally maintaining the circuit open but having a contact adapted to close the circuit momentarily at each oscillation, a relay in the circuit at the substation, a switch-contact operated by the relay adapted to complete the circuit of the line through the relay independent of the telephone-switch, a local locking-circuit for the signal-controlling magnet at the central 'oflice shunting or short-circuiting the relay at the substation, and a contact operated by said signal-controlling magnet for closing said local circuit, whereby the operation of the telephone-switch brings about the continuous display of the line-signal, and the relay at the substation is shunted by the switch-contact operated by said line-signal and deprived of current.

4. The combination with a telephone-line extending from a substation to a central oflice, of a telephone-switch at the substation having a contact closed momentarily as the telephone is removed from the switch or replaced thereon, a call-bell at the substation,- a source of calling-current, a ringing-key at the central oflice adapted when operated to apply the calling-current to the line, a detent adapted to hold said key in its operative position, a tripping-magnet an adapted to withdraw said detent to release the ringing-key and cut ofi the calling-current, said magnet being responsive to the momentary closure of the line-circuit as the substation-telephone is taken for use, a supervisory signal controlled by magnet m, a battery and switch-contacts closed by the ringing-key as it is released, for connecting said magnet m and the battery together in the linecircuit, the magnet being thereafter responsive to the momentary closure of the line as the substation-telephone is replaced on its switch, whereby a disconnect-signal is transmitted.

5. The combination with a telephone-line extending froma substation to a central office, of a telephone-switch at the substation having a contact controlling the line-circuit, said contact being closed momentarily as the telephone is removed from the switch or replaced thereon, a call-bell at the substation in a branch independent of said contact, a source of calling-current, a ringing-key at the central ofiice adapted to be set to apply the calling-current to the line, a tripping-magnet m, and mechanism controlled thereby for releasing the ringing-key, said magnet being responsive to the momentary closure of the line-circuit as the substation-telephone is taken for use, a supervisory signal controlled by said magnet m, a battery and switch-contacts closed by the ringing-key as it is released, for connecting said magnet m and the battery together in the line-circuit, the magnet being thereafter responsive to the momentary closure of the line as the substation-telephone is.replaced on its switch,a relay at the substation,switch-contacts operated by the relay for closing the circuit independently of the telephone-switch, and a short circuit of the relay closed by the telephone-switch when the latter is relieved of the telephone.

6. Acombined ringing-key and supervisory signal for switchboard cord-circuits, comprising circuit-changing switch-contacts, an actuating device therefor, a detent adapted to engage said actuating device to set the same, an electromagnet, a movable armature therefor mechanically connected with said detent to withdraw the same and release the actuating device of the switch, and a signal or target m moved by said armature, whereby after the actuating device has been set the first movement of the armature will release the switch, and subsequent movements thereof will cause the display of the target or indicator independent of the switch, as set forth.

In witness whereof I hereunto subscribe my name this 23d day of October, A. D. 1901.

CHARLES E. SCRIBNER.

Witnesses;

EDWIN H. SMYTIIE, ELLA EDLER. 

